The present invention relates to forming multilayer electronic components using microwave radiation, and more particularly, certain embodiments relate to forming multilayer electronic components using microwave radiation in the presence of a partially reducing atmosphere.
Multilayer electronic devices such as capacitors typically include alternating layers of a dielectric material and a metal electrode material. In order to form a dense structure, the dielectric material is typically fired at high temperatures such as 1300-1400xc2x0 C., in order to sinter the dielectric material. Due to the elevated temperatures needed to sinter the dielectric and the reactive nature of many metals, the metal electrodes are typically formed from palladium (Pd), palladiumxe2x80x94silver (Pdxe2x80x94Ag) alloys, or platinum (Pt). Unfortunately, such electrode materials are expensive and drive up the cost of the components considerably.
Within the multilayer capacitor industry there is a desire to seek out alternative metal materials to lower the cost of the devices. For example, there is a trend to move toward base metal electrodes such as Ni or Cu replacing the more expensive Agxe2x80x94Pd, Pd, and Pt inner electrode devices. With this change, many new processing steps and formulations are required to prevent the reduction of the properties of the ceramic material. When using the base metal inner electrodes, the sintering steps have been performed in atmospheres that prevent oxidation of the metal. However, this same atmosphere reduces the ceramics, creating atomic defects and a host of deleterious properties.
Embodiments of the present invention include a process for forming a multilayer electrical device. The process includes providing a multilayer structure including layers of a dielectric material and an electrode material, the electrode material including at least one material selected from the group consisting of nickel and copper. The dielectric material is sintered by heating the structure using microwaves in an atmosphere having an oxygen partial pressure of no greater than 10xe2x88x922 atm.
Embodiments also include a process for forming an electronic device including a dielectric material and at least one metal electrode. The process includes forming a structure including at least one layer of a base metal electrode material embedded between layers of dielectric material. The structure is microwave heated in an atmosphere containing oxygen at a pressure in the range of 10xe2x88x922 to 10xe2x88x9212 atm, wherein the dielectric material is densified and the base metal electrode remains a metal after the microwave heating.
Embodiments also include a process for forming multilayer capacitors. The process includes providing a first layer of a dielectric material and a second layer of a electrode material including at least one metal selected from the group consisting of nickel and copper. The first and second layers are alternated to form a multilayer structure. The structure is microwave heated in an atmosphere including oxygen at a pressure of no greater than 10xe2x88x922 atm to sinter the dielectric material.